10. LABORATORY ANALYSIS OF FOOD

Food is analysed for many reasons. Some of the key applications of food testing; food

chemical analysis (e.g. moisture, fat, protein, pH, salt, minerals, sugar, contaminants, etc.),

food microbiology analysis (e.g. Lactobacillus, Salmonella, Pseudomonas, Listeria, E. coli,

Staphylococcus aureus, yeast, mould, etc.), food allergen analysis (e.g. peanut, egg, soy,

etc.), food nutrition analysis (determining the nutritional content), natural food toxin

analysis (e.g. histamine), food shelf life studies and food quality control determination (e.g.

GMO analysis, wheat adulteration, etc.).

Food analysis is often provided to ensure food safety. It would be very undesirable

for the both consumer and the manufacturer if unwholesome or toxic products were sold,

hence it is essential that the harmful substances like microorganisms, toxic chemicals or

extraneous matter are absent or effectively eliminated. This should be achieved by observing

good manufacture practice and regulations laid down by the government for specific food

products, as well as using analytical techniques that are capable of detecting unauthorized

substances. Sometimes it is necessary to employ high sensitivity analytical techniques that

can reliably detect very low levels of harmful substances.

Food analysis is conducted by scientists in all major sectors of the food industry

including food manufacturers, ingredient suppliers and by many types of laboratories

(analytical service, national or university research). Different analytical methods are available

for various purposes. They are chosen according to the property to be measured, the type of

foodstuff to be analysed or the reason for testing.

Typically, foods are tested in laboratories to determine their safety for consumption,

composition or to help food manufacturers in understanding the shelf life and stability of a

food product or ingredient. Every laboratory should be lit and ventilated properly, with

appropriate room temperature for a consistent environment and large enough to

accommodate all the necessary equipment as well as to provide a comfortable work area.

Although there are many types of laboratories corresponding to various purposes, every

laboratory has certain components that are common to all. Such equipment includes sinks

with a source of running water where specimens and reagents are rinsed, drained or stained,

and fluids are discarded. Sufficient storage space such as drawers and cabinets must be

available for reagents and supplies, to prevent clutter on the laboratory counter space. As

some reagents or specimens must be kept cool or frozen, a refrigerator and freezer are

essential. One of the necessary things for a laboratory in the 21st century is Internet access,

as it offers the possibility of e-mail to report the critical results of submitted diagnostic tests

or send photographic images. The Internet may also serve as a diagnostic aid in laboratories

with digital camera attachments to compound microscopes. Another important category of

laboratory equipment comprises laboratory glassware such as beakers, graduated cylinders,

flasks, thermometers, reagent bottles, test tubes, glass rods, evaporating dishes, watch

glasses and the like. Central to food testing analysis are spectrometers, alcohol analyzers,

refractometers, titrators, moisture analyzers, and other standard lab equipment. Specialized

analyzers and meters are also available for specific methods and applications, while others

can be used for various food analysis requirements.

The analysis of food products for the presence of pathogenic microorganisms is one

of the basic steps to control the safety and quality of food. Most of the microorganisms

encountered in the laboratory are potentially pathogenic, thus all specimens should be

handled as potentially contagious. The safety of every person working in the laboratory

depends on strict observance of safety and hygiene rules. Staff must wear personal

protective equipment (PPE) during their work and materials contaminated with potentially

infectious agents must be decontaminated before disposal. Moreover, all accidents must be

reported immediately to the laboratory supervisor or other competent authority.

The first stage of microbiological analysis of food consists in taking and preparing a

sample for testing. Incorrect sampling may result into obtaining false negative or false

positive results. The “representative sample” should reflect the profile of the product from

which it originates as accurately as possible.

There are a variety of methods used for microbe detection; some of them being more

traditional, like culture collection, whereas, others are newer and faster and include e.g.

polymerase chain reaction (PCR), infrared devices that detect bacteria in food, and rapid

scans that detect bacterial contamination in blood platelets. One traditional technique of

bacterial detection is to take a sample, grow a bacteria culture, and count the bacteria that

grow. This method is effective but can take hours or days to show results and may miss some

types of bacteria. Another traditional culture method detects changes in oxygen levels

indicating the presence of bacteria but obtaining results can take seven days.

Among the newer, more rapid systems to detect bacteria are: solid-phase cytometry

which detects and counts all fluorescently labelled bacteria within three minutes, or PCR

(polymerase chain reaction) typically required for high sensitivity, specificity, and rapid

results. It is an enzymatic reaction replicating a DNA molecule, thus a critical condition of the

PCR course is the presence of an enzyme, thermostable DNA polymerase. Variants of the

conventional PCR method are a real-time PCR (an improved method observed in real time)

and multiplex PCR (two or more loci are simultaneously amplified in the same reaction).

Task. Answer the following questions.

What types of food analysis do you know?

___________________________________________________________________________

Who conducts food analysis?

___________________________________________________________________________

What is a laboratory?

___________________________________________________________________________

What typical equipment and instruments can you name?

___________________________________________________________________________

Are there some tools or appliances necessary for food testing?

___________________________________________________________________________

What does the abbreviation PPE stand for?

___________________________________________________________________________

What is a “representative sample”?

___________________________________________________________________________

Can you name some rapid methods of detecting microorganism in food?

___________________________________________________________________________

What does the word “thermostable” mean?

___________________________________________________________________________

Useful phrases and expressions

Basic laboratory equipment /ˈbeɪsɪk ləˈbɒrət(ə)ri ɪˈkwɪpmənt/Základní vybavení laboratoře

balance/scales /ˈbæləns/ /skeɪls/ váhy

beaker /ˈbiːkə(r)/ kádinka

boiling flask /ˈbɔɪlɪŋ flɑːsk/ varná baňka

Bunsen burner /ˌbʌns(ə)n ˈbɜː(r)nə(r)/ Bunsenův kahan

burette /bjuəˈret/ byreta

crucible /ˈkruːsəb(ə)l/ tavicí kelímek

Erlenmeyer flask/conical flask/ˈɜːlənˌmaɪə flɑːsk / /ˈkɒnɪk(ə)l…/ Erlenmeyerova baňka

evaporating dish /ɪˈvæpəreɪtɪŋ ˌdɪʃ/ odpařovací miska

forceps /ˈfɔː(r)seps/ kleště

funnel /ˈfʌn(ə)l/ nálevka

glass rod /ɡlɑːs rɒd/ skleněná tyčinka

graduated cylinder /ˈɡrædʒuˌeɪtɪd ˈsɪlɪndə(r)/ odměrný válec

hand lens/magnifying glass /hænd lenz/ /ˈmæɡnɪfaɪŋ ɡlɑːs/ lupa

microscope /ˈmaɪkrəˌskəʊp/ mikroskop

mortar and pestle /ˈmɔː(r)tə(r) ənd ˈpes(ə)l/ třecí miska s tloučkem

pipette/chemical dropper /pɪˈpet/ /ˈkemɪk(ə)l ˈdrɒpə(r)/ pipeta

ring stand/clamp stand /rɪŋ stænd / /klæmp stænd/ laboratorní stojan

test tube holder /test tjuːb ˈhəʊldə(r)/ držák na zkumavky

test tube /test tjuːb/ zkumavka

thermometer /θə(r)ˈmɒmɪtə(r)/ teploměr

tongs /tɒŋz/ kleště

tripod /ˈtraɪpɒd/ trojnožka

wash bottle /wɒʃ ˈbɒt(ə)l/ střička

watch glass /wɒtʃ ɡlɑːs/ hodinové sklíčko

wire gauze /ˈwaɪə(r) ɡɔːz/ drátěná síťka

Equipment and instruments specific Zařízení a nástroje specifické

for the microbiology laboratory pro mikrobiologické laboratoře

syringe and needle /sɪˈrɪndʒ ˈniːd(ə)l/ stříkačka a jehla

inoculating loops /ɪˈnɒkjʊleɪtɪŋ luːps/ očkovací kličky

scissors and forceps /ˈsɪzə(r)z ənd ˈfɔː(r)seps/ nůžky a kleště

sterile cotton-tipped swabs /ˈsteraɪl ˈkɒt(ə)n tɪpt swɒb/ sterilní štětička

collection tube /kəˈlekʃ(ə)n tjuːb/ odběrové zkumavka

glass slide and cover tip /ɡlɑːs slaɪd ənd ˈkʌvə(r) tɪp/ podložní a krycí sklíčko

various culture media /ˈveəriəs ˈkʌltʃə(r) ˈmiːdiə/ různá kultivační média

gram stain /ɡræm steɪn/ Gramovo barvení

incubator /ˈɪŋkjʊˌbeɪtə(r)/ inkubátor

discard jar with disinfectant odpadní nádoba s

/dɪsˈkɑː(r)d dʒɑː(r) wɪð ˌdɪsɪnˈfektənt/ desinfekcí

Lab. personal protective equipment (PPE) Osobní ochranné pomůcky

laboratory coat/gown /ləˈbɒrət(ə)ri kəʊt / /...ɡaʊn/ laboratorní plášť

safety goggles /ˈseɪfti ˈɡɒɡ(ə)lz/ ochranné brýle

face shield /feɪs ʃiːld/ ochranný štít

disposable gloves /dɪˈspəʊzəb(ə)l ɡlʌvz/ jednorázové rukavice

face mask/respirator / feɪs mɑːsk//ˈrespəˌreɪtə(r)/ obličejová maska

Units used to describe lab results Jednotky užívané pro popis lab. výsledků

g/L or g/l (gram per litre/liter)/ɡræm pə(r) ˈliːtə(r)/ gram na litr

L/L (litres per litre) /ˈliːtə(r) pə(r) ˈliːtə(r)/ litr na litr

U/L (unit per litre) /ˈjuːnɪts pə(r) ˈliːtə(r)/ jednotka na litr

mmol/L (millimole per litre) /ˈmɪləˌmoːl pə(r) ˈliːtə(r)/ milimol na litr

umol/L (micromols per litre) /ˈmaɪkrəʊˌməʊl pə(r) ˈliːtə(r)/ mikromol na litr

Terms used to describe lab values Termíny užívané pro popis lab. výsledků

within normal limits/normal /wɪðˈɪn ˈnɔː(r)m(ə)l ˈlɪmɪts/ v normě/normální

elevated/raised/increased /ˈeləˌveɪtɪd/ /reɪzd/ /ɪnˈkriːst/ zvýšený

reduced/decreased /rɪˈdjuːst//diːˈkriːst/ snížený

Vocabulary practice

1. Label the following laboratory equipment.

a long thin glass container that is open at one end and is used in laboratories T……. T……….

a glass tube marked with a scale and with a tap at the bottom B………………..

a tube wide at the top and narrow at the bottom, used for pouring liquid F………………..

a piece of equipment used for weighing people or things S…………………

a glass or plastic container with straight sides B………………..

a bowl in which you crush substances into a powder M………………

a container used for heating substances or melting metals C………………..

special glasses that protect your eyes G……………….

a piece of equipment producing a gas flame, used for scientific experiments B………B………

an object with three legs that is used for supporting something T…………………

2. Translate the following phrases into English.

provádět pokusy a výzkum ………………………………………………………………………………..

objevit nebezpečné bakterie ………………………………………………………………………………..

zkoumat přítomnost enzymu ………………………………………………………………………………..

řádně odebrat vzorek ………………………………………………………………………………..

zvýšené hodnoty bílkovin ………………………………………………………………………………..

analýza na potravinové alergeny ………………………………………………………………………………..

vypěstovat bakteriální kulturu ………………………………………………………………………………..

sledovat změny v hodnotách kyslíku ………………………………………………………………………………..

získat výsledky během pár minut ………………………………………………………………………………..

nebezpečí falešně pozitivních výsledků.……………………………………………………………………………..

Below are the steps describing the procedure for operating a microscope. Put them into the

correct order.

1. Place the slide on the stage.

2. Lower the stage to its lowest point.

3. Turn on the light.

4. Move the objective into position by turning the turret or revolving nosepiece.

5. Go home

6. Use the coarse and fine adjustment knobs to get the image into focus.

7. Remove the slide.

8. Adjust the condenser and the diaphragm following the manufacturer’s instructions.

9. Check the eyepieces, objectives and condenser lens and clean them if necessary.

10. Turn the light off and lower the stage completely.

Grammar Practice - Reported (Indirect) Speech

Key points:

Back shift : Tenses shift back in time after a past tense reporting verb. Present

present simple past simple

I work in a laboratory.

Pracuji v laboratoři.

He said he worked in a laboratory.

Řekl, že pracuje v laboratoři.

present continuous past continuous

I am working in a laboratory. He said he was working in a laboratory.

present perfect simple past perfect simple

I have worked in a laboratory. He said he had worked in a laboratory.

present perfect continuous past perfect continuous

I have been working in a laboratory. He said he had been working in a laboratory.

Past

past simple past perfect simple/past simple

I worked in a laboratory.

Pracoval jsem v laboratoři.

He said he had worked/ worked in a laboratory.

Řekl, že pracoval v laboratoři.

past continuous past perfect continuous

I was working in a laboratory. He said he had been working in a laboratory.

past perfect simple/continuous past perfect simple/continuous - NO CHANGE!!!

I had worked/been working in a

laboratory.

He said he had worked/been working in a

laboratory.

Future

Will Would

I will work in a laboratory.

Budu pracovat v laboratoři.

He said he would work in a laboratory.

Řekl, že bude pracovat v laboratoři.

“be going to” “was/were going to”

I am going to work in a laboratory. He said he was going to work in a laboratory.

Modal verbs

can could

I can work in a laboratory. He said he could work in a laboratory.

may might

I may work in a laboratory. He said he might work in a laboratory.

will would

I will work in a laboratory. He said he would work in a laboratory.

shall would

I shall work in a laboratory. He said he would work in a laboratory.

must must or had to

I must work in a laboratory. He said he must/had to work in a laboratory.

needn’t needn’t/didn’t have to

I needn’t work in a laboratory. He said he needn’t/didn’t have to work in a

laboratory.

Reference words (place and time adverbials, pronouns, etc.)

Direct speech Reported speech

now then, at the moment

today, this week, this month, etc. that day, that week, that month

yesterday, last week, last year, etc. the day before, the previous week, the previous

year

tomorrow, next week the following day, the following week

ago before

here there

Indirect questions

Reporting questions - Yes/No questions are reported using if. The verb does not have a

question form but has the form of a normal statement. There is no question mark.

e.g. “Do I have to wear a lab coat during the experiment?”

He asked me if he had to wear a lab coat during the experiment.

Wh- questions are reported using the question word. The verb has the form of a normal

statement. There is no question mark.

e.g. Why do I have to wear a lab coat during the experiment?”

He asked me why he had to wear a lab coat the experiment.

No back shift: If the reporting verb is in the present tense.

e.g. “I sample the blood if necessary.”

The doctor says he samples the blood if necessary.

If the present (e.g. today) in the direct speech is still the present in the reported speech.

e.g. “I am in a lab.”

He said he is in a lab today.

If the future in the direct speech is still the future in the reported speech.

e.g. “I will phone you the results.”

He said he will phone me the results. (I am still waiting for his phone call).

If the reported words are always true.

e.g. “Salmonellosis is an infection with bacteria called Salmonella.”

He said salmonellosis is an infection with bacteria called Salmonella.

If the sentences are commands (imperatives) or requests; they are reported with tell or ask + infinitive.

e.g. “Avoid distress and suffering to the experimental animals!”

He told us to avoid distress and suffering to the experimental animals.

SAY x TELL

We say something – e.g. I said I could treat his wound.

We tell somebody – e.g. I told him I could treat his wound.

1. Rewrite each sentence as reported speech. Start with “the supervisor

said/asked/ordered, etc”.

The diagnosis is based on laboratory criteria of salmonella infection.

___________________________________________________________________________

The reference laboratory will build up and store diagnostic agents.

___________________________________________________________________________

The handling of live FMD virus for research has been carried out only in the approved

laboratory.

___________________________________________________________________________

Look it up in the Manual of Standards for Diagnostic Tests and Vaccines!

___________________________________________________________________________

Laboratory waste was categorised in specific waste groups yesterday.

___________________________________________________________________________

Are you cooperating with any medical laboratory technicians these days?

___________________________________________________________________________

Where did you buy all the equipment for laboratory diagnostics?

___________________________________________________________________________

Can we recruit more laboratory assistants next week?

___________________________________________________________________________

The tests must comply with the relevant requirements for the protection of laboratory

animals.

___________________________________________________________________________

What do you know about research laboratories?

___________________________________________________________________________

2. Underline the most suitable verb form in each sentence. Sometimes both possibilities are

correct.

1. The manager asked me if the food producer would need some time to test the meat

products.

The manager asked: “Does the food producer need/Will the producer need some time

to test the meat products?”

2. My colleague told me the raw milk had been exposed to microbial contamination.

My colleague said: “The raw milk was exposed/has been exposed to microbial

contamination.”

3. They told us to ensure that foodstuffs are not contaminated.

“Ensure/You ensure that foodstuffs are not contaminated!”

4. The laboratory workers told us that Listeria is one of the few bacteria that are able to

multiply in the refrigerator.

They said: “Listeria is able/will be able to multiply in the refrigerator.”

5. The inspector asked them who might be responsible for the research.

The inspector asked:” Who may be/must be responsible for the research?”

3. Translate the sentences into English.

Pohrozil nám, že kontrola bude provedena bez předchozího upozornění.

……………………………………………………………………………………………………………………………………………....

Hospodář prokázal, že porážka byla nevyhnutelná.

……………………………………………………………………………………………………………………………………………....

Ředitel musel připustit, že členské státy reagovaly velmi pozitivně.

……………………………………………………………………………………………………………………………………………....

Zeptali se nás, zda mrtvá těla všech volně žijících zvířat s pozitivním nálezem slintavky a

kulhavky jsou zpracována pod úředním dozorem.

……………………………………………………………………………………………………………………………………………....

……………………………………………………………………………………………………………………………………………....

Inspekční úředník rozhodl, že vzorky budou uchovány v chladničce po dobu alespoň 5 hodin.

……………………………………………………………………………………………………………………………………………....

Odpověděl, že zvířata nechce převážet v železničním voze.

……………………………………………………………………………………………………………………………………………....

Vocabulary

accommodate (v) /əˈkɒmədeɪt/ vyhovovat, přizpůsobit

adjust (v) /əˈdʒʌst/ seřídit, nastavit

agar (n) /ˈeɪɡɑː(r)/ agar

allergen (n) /ˈælə(r)ˌdʒen/ alergen

analyser (n) /ˈænəlaɪzə/ analyzátor, analytik

beaker (n) /ˈbiːkə(r)/ kádinka

cabinet (n) /ˈkæbɪnət/ skříňka

clutter (n) /ˈklʌtə(r)/ nepořádek

contaminant (n) /kənˈtæmɪnənt/ znečišťující látka

count (n) /kaʊnt/ množství, počet ve vzorku

counter space (phr) /ˈkaʊntə(r) speɪs/ pracovní prostor

current (n) /ˈkʌrənt/ proud

cylinder (n) /ˈsɪlɪndə(r)/ válec

decontaminate (v) /ˌdiːkənˈtæmɪˌneɪt/ dekontaminovat, odmořit

demonstrate (v) /ˈdemənˌstreɪt/ prokázat, předvést

discard (v) /dɪsˈkɑː(r)d/ vyhodit

disposal (n) /dɪˈspəʊz(ə)l/ likvidace

drain (v) /dreɪn/ odtéct, vylít

drawer (n) /ˈdrɔːə(r)/ zásuvka, šuplík

encounter (v) /ɪnˈkaʊntə(r)/ setkat se s, narazit na

extraneous (adj) /ɪkˈstreɪniəs/ nepodstatný; vnější

eyepiece (n) /ˈaɪˌpiːs/ okulár (mikroskop)

flask (n) /flɑːsk/ baňka

harmful (adj) /ˈhɑː(r)mf(ə)l/ škodlivý

histamine (n) /ˈhɪstəmiːn/ histamin

image (n) /ˈɪmɪdʒ/ snímek, obrázek

Lactobacillus /ˌlæktəʊbəˈsɪləs/ laktobacil

Listeria /lɪsˈtɪərɪə/ listerie

meter (n) /ˈmiːtə(r)/ měřicí přístroj

moisture (n) /ˈmɔɪstʃə(r)/ vlhkost

peanut (n) /ˈpiːˌnʌt/ arašíd

platelet (n) /ˈpleɪtlət/ krevní destička

polymerase (n) /pəˈlɪməreɪz/ polymeráza

Pseudomonas /sjuːˈdɒmənəs/ pseudomonáda

reagent (n) /riˈeɪdʒ(ə)nt/ činidlo, reagens

reflect (v) /rɪˈflekt/ odrážet

revolving nosepiece (phr) /rɪˈvɒlvɪŋ ˈnəʊzˌpiːs/ otočná hlavice mikroskopu

rinse (v) /rɪns/ opláchnout

rod (n) /rɒd/ tyčinka

running water (phr) /ˈrʌnɪŋ ˈwɔːtə(r)/ tekoucí voda

sink (n) /sɪŋk/ umyvadlo, výlevka

slide (n) /slaɪd/ podložní sklíčko

specimen (n) /ˈspesəmɪn/ vzorek

spectroscopy (n) /spekˈtrɒskəpɪ/ spektroskopie

stage (n) /steɪdʒ/ stolek (mikroskop)

stain (v) /steɪn/ vybarvovat (preparáty)

Staphylococcus aureus /ˌstæfɪləʊˈkɒkəs ˈɔːrɪəs/ zlatý stafylokok

submit (v) /səbˈmɪt/ předložit, podat, odevzdat

test tube (n) /test tjuːb/ zkumavka

thermometer (n) /θə(r)ˈmɒmɪtə(r)/ teploměr

thermostable (adj) /ˌθɜːməʊˈsteɪbəl/ odolný proti teplu

tripod (n) /ˈtraɪpɒd/ stativ, trojnožka

turret (n) /ˈtʌrɪt/ revolverová hlava (mikroskop)

unwholesome (adj) /ʌnˈhəʊls(ə)m/ nezdravý, zdravý škodlivý

wagon (n) /ˈwæɡən/ nákladní vagón, vůz